30 gwei is the amount of wei you spend for each unit of gas. At 200,000 gas, you have 6 x 10^15 wei, which is 0.006 Ether, or about $1.10 in fees at $180 per Ether. Any gas that isn't spend on the transaction will be refunded to you automatically though. I recommend checking out this post I wrote about Ethereum Gas if you want more info on how it works and how to calculate it.